Should I Pressure Wash My Roof?
The Direct Answer — And What to Do Instead
Quick Answer
No. You should not pressure wash your roof.
Served by Roof Labs Canada — Vancouver Island roof preservation specialists. No roof walking. No wire brushes. No pressure washing. (250) 889-8490
No. You should not pressure wash your roof. This is the position of every major asphalt shingle manufacturer (IKO, GAF, BP, Certainteed), the Western Red Cedar Lumber Association for cedar roofs, the Roofing Contractors Association of BC, and professional biocide applicators across Vancouver Island. The reasons are specific and structural — not a matter of opinion.
What Pressure Washing Actually Does to Your Roof
High-pressure water (2,000–4,000 PSI) on asphalt shingles physically dislodges ceramic granules from the asphalt binder. Granule loss is permanent and irreversible — shingles cannot regenerate their protective coating. The result: bare asphalt zones that oxidise rapidly under UV, cracking and failing years earlier than untreated shingles. On cedar shakes, high pressure splits wood fibres, opening moisture pathways to the shake core, accelerating brown rot, and permanently weakening the shake structure. Beyond physical damage, pressure washing doesn't solve the biological problem — moss rhizoids remain in the shingle after surface cleaning, and regrowth typically occurs within 60–90 days.
What to Do Instead
Professional soft washing combined with biocide chemistry is the correct method. Soft washing uses water at under 200 PSI — similar to a garden hose — as the delivery vehicle for professional biocide solutions. The chemistry does the cleaning work by killing moss, algae, and lichen at the biological level. No granule loss. No fibre splitting. No structural damage. And genuine 2+ year results from the residual barrier left in the shingle. Roof Labs Canada uses professional soft wash equipment exclusively — no pressure washers.
Frequently Asked Questions
My roof looks clean after pressure washing. Didn't it work?
Visually, yes — temporarily. Pressure washing removes surface moss for approximately 60–90 days. The physical damage to granules is happening in the background but isn't visible yet. Within 3 months, moss regrows from undamaged rhizoids, and granule depletion becomes visible as the stripped areas darken. The "clean" result from pressure washing is real but short-lived and comes with permanent damage.
Roof Preservation Knowledge Base
About Roof Labs Canada
Roof Labs Canada is Vancouver Island's roof preservation and surface intelligence company — providing biocide treatment, biological growth elimination, and surface protection for asphalt and cedar roofing systems. As Roof Labs Canada, we bring marine-engineered formulas, 9+ years of island experience, and a written 2-year guarantee to every project.
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Why Choose Us
Science-Based Treatment
Biocide protocols calibrated to island biology
2-Year Written Guarantee
Free return if moss comes back
9+ Years Island Experience
966+ roofs treated
Licensed & Fully Insured
Fully certified in BC
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Roof Preservation. Vancouver Island.
Professional treatment. 2-year guarantee. Marine climate engineered.
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Contact Information
Phone
(250) 889-8490Service Area
Greater Victoria, BC
Sidney, Saanich, Langford
and surrounding areas
Business Hours
Monday - Friday: 8:00 AM - 6:00 PM
Saturday: 9:00 AM - 4:00 PM
Sunday: Closed